Change msleep() and tsleep() to not alter the calling thread's priority

if the specified priority is zero.  This avoids a race where the calling
thread could read a snapshot of it's current priority, then a different
thread could change the first thread's priority, then the original thread
would call sched_prio() inside msleep() undoing the change made by the
second thread.  I used a priority of zero as no thread that calls msleep()
or tsleep() should be specifying a priority of zero anyway.

The various places that passed 'curthread->td_priority' or some variant
as the priority now pass 0.

1 files changed, 1 insertions, 3 deletions

diff --git a/sys/vm/vm_zeroidle.c b/sys/vm/vm_zeroidle.c
index 68babd0..683990f 100644
--- a/sys/vm/vm_zeroidle.c
+++ b/sys/vm/vm_zeroidle.c
@@ -140,9 +140,7 @@ vm_page_zero_idle_wakeup(void)
 static void
 vm_pagezero(void __unused *arg)
 {
-	struct thread *td;
 
-	td = curthread;
 	idlezero_enable = idlezero_enable_default;
 
 	for (;;) {
@@ -159,7 +157,7 @@ vm_pagezero(void __unused *arg)
 			vm_page_lock_queues();
 			wakeup_needed = TRUE;
 			msleep(&zero_state, &vm_page_queue_mtx,
-			    PDROP | td->td_priority, "pgzero", hz * 300);
+			    PDROP, "pgzero", hz * 300);
 		}
 	}
 }